“
An upshot of Mach’s philosophy of science, and one he does not fail to notice himself, is that the unobservable ‘posits’ of our scientific theories, items such as atoms, electrons, fields and waves, cannot be accorded any substantial existence. Indeed, Mach says to accord any material status to such concepts is to invoke ‘the sham ideas of the old metaphysics’. The idea is resurgent in Quine, who claims the posits of our physical theory have no greater epistemological footing than ‘Homer’s gods’.
”
”